package main

import (
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"html/template"
	"io/ioutil"
	"os"

	"./util"
)

func handleErr(err error, str string, a ...interface{}) {
	a = append([]interface{}{err}, a...)
	if err != nil {
		fmt.Fprintf(os.Stderr, str, a...)
		os.Exit(1)
	}
}

func handleBool(ok bool, str string, a ...interface{}) {
	if !ok {
		fmt.Fprintf(os.Stderr, str, a...)
		os.Exit(1)
	}
}

var tmpl = template.Must(template.New("pem2html").
	Funcs(template.FuncMap{
		"htmlcell": util.HTMLCellEscapeString,
	}).Parse(`<table class=diff>
  <tr class="diff-del"><td colspan=4>--- tls.pem</td></tr>
  <tr class="diff-add"><td colspan=4>+++ crtsh.pem</td></tr>
  <tr class="diff-dat"><td colspan=4>@@ -1,{{.nTLS}} +1,{{.nCrtSh}} @@</td></tr>
{{range $cert := .certs}}
  <tr class={{$cert.Class}}>
    <td><a href="{{$cert.Url}}">{{$cert.Pfix | htmlcell}}</a></td>
    <td><a href="{{$cert.Url}}">{{$cert.X509.Subject.CommonName | htmlcell}}</a></td>
    <td><a href="{{$cert.Url}}">{{$cert.X509.NotBefore.Local.Format "2006-01-02 15:04:05"}}</a></td>
    <td><a href="{{$cert.Url}}">{{$cert.X509.NotAfter.Local.Format "2006-01-02 15:04:05"}}</a></td>
  </tr>
{{end}}
</table>
`))

type Cert struct {
	Url    string
	action string
	X509   *x509.Certificate
}

func (cert Cert) Pfix() string {
	return map[string]string{
		"add": "+",
		"del": "-",
		"ctx": " ",
	}[cert.action]
}

func (cert Cert) Class() string {
	return "diff-" + cert.action
}

func main() {
	data, err := ioutil.ReadAll(os.Stdin)
	handleErr(err, "Error reading stdin: %v\n")

	var certs []Cert
	a := 0
	b := 0
	for len(data) > 0 {
		var certPem *pem.Block
		certPem, data = pem.Decode(data)

		var ok bool
		var cert Cert

		cert.Url, ok = certPem.Headers["X-Crt-Sh-Url"]
		handleBool(ok, "Did not get X-Crt-Sh-Url\n")

		cert.action, ok = certPem.Headers["X-Diff-Action"]
		handleBool(ok, "Did not get X-Diff-Action\n")
		switch cert.action {
		case "add":
			b++
		case "del":
			a++
		case "ctx":
			a++
			b++
		default:
			handleBool(false, "Unknown X-Diff-Action: %q\n", cert.action)
		}

		cert.X509, err = x509.ParseCertificate(certPem.Bytes)
		if err != nil {
			cert.X509 = new(x509.Certificate)
		}

		certs = append(certs, cert)
	}

	handleErr(tmpl.Execute(os.Stdout, map[string]interface{}{
		"certs":  certs,
		"nTLS":   a,
		"nCrtSh": b,
	}), "Could not execute template: %v\n")
}